Zeolites are crystalline aluminosilicate minerals of a cage-network structure with pores a few angstroms in diameter. Some of the common materials, such as zeolite Y (faujasite) or zeolite A have a three dimensional structure with pore intersections ("supercages") somewhat larger than the pore size. Others such as zeolite L have channels with diffusional cross connections. Zeolites are useful as shape selective adsorbents for a variety of organic molecules and shape selective catalysts for a variety of chemical processes.
Levels of hydration of zeolites determine the number of Si-OH and Al-OH species present. The interaction of such hydroxyl groups with the aluminum oxide centers is generally thought to yield protonic (Bronsted) acid sites, while the aluminum oxide centers themselves and the exchanged cations are capable of serving as electron acceptor (Lewis acid) sites. Normal zeolitic materials have acid activity, and even if they are neutralized with base, such as with the conversion of H-zeolite to Na-zeolite, they retain some acid character. Some references consider zeolites exchanged with alkali metal cations to have some soft base sites, with an excess of acidic sites and some basic sites coexisting simultaneously. See, for example, Barthomeuf et.al; "Basicity and Basic Catalytic Properties of Zeolites", Materials Chemistry and Physics, 18 (1988) 553-575. Further see Unland et.al; U.S. Pat. No. 4,140,726, issued Feb. 20, 1979, particularly at column 5, lines 39-44. However, neither of these references teach the use of alkaline earth metal compounds in conjunction with a zeolite wherein the amount of alkaline earth metal present exceeds that required to provide a fully metal cation-exchanged zeolite. The acidic properties of zeolites allow them to be used to catalyze acid-catalyzed reactions such as cracking, rearrangements, alkylation of aromatic rings, etc. However, since all known zeolites, including ion exchanged materials, exhibit acid catalytic properties, it would thus be of considerable economic importance to produce materials having the narrow channels and potential for shape selective catalysis of zeolites wherein the basic properties of such materials predominated over the acidic properties, if any, present in the materials. Such materials would be useful for a variety of reactions such as side chain alkylation of aromatics, olefin oligomerization, selective oxidation, condensations and double bond isomerization without skeletal rearrangement which are difficult to achieve with normal acid zeolites.